Polyurethane coated fabric filled with isocyanate free elastomer and method of making same



April 9, 1963 J. A. PORTEOUS 3,085,027

POLYURETHANE COATED FABRIC FILLED WITH ISOCYANATE FREE ELASTOMER AND METHOD OF MAKING SAME Filed Jan. 50, 1961 HIII gill .LLLIL IN VEN TOR. dd/f/V ,4. l d/77500:)

ATTORNEY POLYURETHANE CQATED FABRIC FILLED WlTH ISQCYANATE FREE ELASTUMER AND METHDD 6F MAKENG SAME John A. Porteous, Montreal, Quebec, (Ianada, assignor to United States Rubber Company, New York, N.Y., a corporation of New .iersey Filed Jan. 30, 1961, Ser. No. 85,611 9 Claims. (Cl. 117-68) This invention is concerned with an improved coated fabric and more particularly to an improved fabric coated with a polyurethane elastomer, as well as to a method of making such a coated fabric.

Woven fabrics of the type fully disclosed in United States Patent No. 2,619,705 to Foster are known to have high tear-resistance. Such fabrics are woven from yarns or strands of strong continuous filaments which are essentially untwisted so that the filaments flatten out like minute ribbons in the fabric. When such a fabric is subjected to a force tending to tear it, the flat yarns shift in the weave to crowd together thereby providing a compact group of yarns having the tear resistance of several such yarns. it is this shifting or movement of the flat yarns under stress, so as to resist a force which might break a single yarn, that is responsible for the high tear-resistance of such fabrics.

It has been proposed to coat such fabrics with polyurethane elastomers, as in United States Patent No. 2,721,811 to Dacey et al., so as to combine the high abrasion resistance of such elastomers with the high tear resistance of the above-mentioned fabrics. polyurethane elastomers is further desirable from the standpoint that it provides a lower gauge coating, which is lightweight and high strength, as compared to other elastomeric coatings. However, it has been found that polyurethane coatings adhere to the yarns of such fabrics to such an extent as to prevent movement of the yarns when subjected to a tearing force thereby resulting in a coated fabric that has lower tear resistance than the uncoated fabric per se. As the filaments of such fabrics are composed of materials having more than two isocyanate-reactive groups (i.e., at least one active hydrogen atom per group) and as the polyurethane elastomers contain unreacted isocyanate groups and/or excess organic diisocyanates, it appears that the undesirable degree of adhesion attained with such polyurethane coated fabrics is due to the reaction of such filament reactive groups with the excess or unreacted isocyanate contained in the polyurethane composition. The fact that filaments such as nylon (a synthetic linear polyamide which contains a plurality of isocyanate-reactive carbonamide groups in the polymer chain) react with diisocyanate is supported by the disclosure of United States Patent No. 2,763,624 to Newell and United States Patent No. 2,333,- 914 to Berchet.

Accordingly, an object of this invention is to provide a polyurethane coated fabric that is highly tear-resistant.

Another object of this invention is to provide a coated fabric in which the textile fabric and coating cooperate to form a waterproof fabric that is highly tearresistant, as well as being light in weight, low in gauge and high in strength.

The use of Patented Apr. 9, 1963 ice The manner in which the invention accomplishes the foregoing objects, as well as additional objects and advantages, will be made clear in the following detailed description, which is intended to be read with reference to the accompanying drawings, wherein:

FIG. 1 is a face view on an enlarged scale of a small piece of uncoated fabric to be employed in the practice of this invention; and FIG. 2 is a sectional view on a still larger scale taken on line 2-2 of FIG. 1 after the fabric has been coated in accordance with the teacings of this invention.

According to the instant invention, the fabric which is composed of yarns containing a plurality of isocyanatereactive groups is first coated on one side with a flexible elastomeric sealing material which is free of isocyanate groups so as to penetrate the interstices of the fabric and thereafter coated on the other side with a polyurethane composition. As the sealing material will not react with the isocyanate-reactive groups of the fabric filaments, the degree of adhesion attained will not impair the tear resistance of the fabric. Although the polyurethane composi tion apparently reacts with the fabric filaments, the pres ence of the sealing material in the interstices of the fabric limits such reaction and resulting high adhesion to the tops of the filaments. It has been found that if the adhesion of the polyurethane composition is thus limited to the tops of thefabric filaments, the tear resistance of such a coated fabric will not be less than that of the uncoated fabric but will in fact be greater. Preferably, the sealing material is also free of isocyanate-reactive groups so that chemical bonding with the polyurethane coating will not occur.

As stated above, the fabrics employed in this invention are those disclosed in US. Patent No. 2,619,705. This highly tear-resistant woven fabric is formed of essentially untwisted, continuous multi-filament yarns that are free to flatten out in the fabric like miniature ribbons. By essentially untwisted, it is meant that the yarns have no more than the normal producers twist of one or two turns per inch. The relatively flat untwisted yarns do not contain a bonding agent which would interfere with the free movement of the fibers in the fabric. The flat yarns are disposed in the fabric in close parallel relation to each other and may touch one another but should not abut firmly against each other, as it is important that the yarns be free to spread laterally and move in the fabric.

- This construction provides a somewhat loose weave, so

that when the fabric is subjected to a force tending to tear it, the yarns under the greatest strain can shift in the fabric several yarn rows to cause the stress to fall upon a compact group of such yarns. Each yarn is wider than it is thick so the yarns will lay flat in the fabric and form a smooth face, thin fabric. Each yarn may have thickness of from one to several filaments as desired and have a greater width than thickness. The ratio of the width of the yarn to its thickness preferably is not less than 4 to 1, and may be as great as 15 to 1 or greater in the fabric. A strand may be formed of a single essentially untwisted yarn, or of two or more such yarns laid side by side. As shown in FIG. 1, the fabric has a square weave with one up and one down, but other weaves may be used, and as shown the same size yarns are used in the warp 1t and weft 11, but if desired different size yarns may be used in the warp from those in the weft. These yarns or strands are shown in the drawing as greatly enlarged,

since they are ordinarily not more than a few hundredths of an inch in width and a few thousandths of an inch thick and may be even smaller. The spacing of the yarns permits the crossing yarns to lay very fiat in the woven fabric, and produces small apertures or interstices 13 through the fabric adjacent the cross yarns. Such a flat fabric having the apertures 13 coats well and these apertures are desirable as they permit the sealing material to strike through the apertures and anchor itself strongly to the fabric in an interlocking manner.

The filaments of the fabric employed in this invention contain a plurality of isocyanate-reactive groups, that is, the filaments have more than two groups containing at least one active hydrogen atom per group. Specifically, the isocyanate-reactive groups are either amide or hydroxyl groups. The filaments that contain a plurality of amide groups are nylon (a synthetic linear polyamide having recurring amide groups as an integral part of the polymer chain) and silk (a high tenacity continuous filament containing amide groups). Other continuous, essentially untwisted filaments containing isocyanate reactive amide groups, such as the fine synthetic fibers made from casein and other amino acid compounds (Aralac), may also be used. In general, the fibrous material is an organic fiber containing amide groups or hydroxyl groups at least some of which groups contain an active hydrogen atom. Typical continuous filaments containing such hydroxyl groups are high tenacity viscose rayon and high strength regenerated cellulose of the type made by saponifying acetate rayon and stretching during the processing.

The fabric is preferably formed from nylon filaments, which are long chain, synthetic polymeric amides having recurring amide groups as an integral part of the main polymer chain and which are capable of being formed into filaments in which the structural elements are oriented in the direction of the axis. The nylon polyamides are of the general type described in US. Patents No. 2,071,250, 2,071,253, 2,130,523, and 2,130,948. For the best fiber-forming properties, the polymerization reaction should be continued until the intrinsic viscosity is at least 0.4. These poly amides, generally speaking, comprise the reaction products of a polyamide-forming composition in which the molecules are bifunctional and contain two amide-forming groups, each of which is complementary to an amide-forming group in other molecules in said composition. These polyamides as defined above or as otherwise identified hereinafter can be obtained, for example, by self-polymerization of monoarnino-monocarboxylic acids, or by reacting a diamine with a di-basic carboxylic acid in substantially equi-molecular amounts, it being understood that reference herein to the amino acids, diamines and dibasic carboxylic acids is intended to include the equivalent amide-forming derivatives thereof. On hydrolysis with hydrochloric acid the amino acid polymers yield the amino acid hydrochloride, and the diamine-dibasic acid polymers yield the dial-nine hydrochloride and the dibasic acid. One of the many nylon fibers suitable for use in connection with the present invention is the 6-6 nylon (polyhexamethylene adipamide) which contains an amide group having an active hydrogen atom for every six carbon atoms, and is formed from hex-amethylene diamine and adipic acid. The polyamides contain a plurality of groups of the structure:

Where X is oxygen or sulfur (thioamide) and R is hydrogen or a monovalent hydrocarbon radical. As further examples of synthetic polyamides which can be employed in this invention, there may be mentioned the 6-amino caproic acid polymer, polydecamethylene adipamide, polydecamethylene sebacamide, poly-m-phenylene sebacamide, the 7-amino-heptanoic acid polymer, the 12- amino-stearic acid polymer, as well as other polyamides and interpolyamides of the types mentioned in US. Patents 2,071,253 and 2,130,948. The polyamides may be oriented, e.g., by cold drawing or rolling, prior to treatment and may be modified with other substances, e.g., plasticizers, dyes, pigments, antioxidants; viscosity stabilizers, cellulose derivatives, and resins.

The sealing material 12 can be any flexible, elastomeric composition which can be formed into a film andis free of isocyanate groups, as the only elastomers believed to react with amide or hydroxyl groups are the polyurethanes which contain um'eacted isocyanate radicals. Suitable sealing elastomers will be seen to include rubbers such as natural rubber and synthetic rubbers including neoprene (polychloroprene), butyl rubber, rubbery copolymers of butadiene and acrylonitrile, rubbery copolymers of butadiene and styrene, etc., resins such as plasticized vinyl resins comprising a major proportion of vinyl chloride, e.g., polyvinyl chloride and copolymers of a major proportion of vinyl chloride and a minor proportion of a monomer copolymerizable therewith such as vinyl acetate, dialkyl maleates (e.g. diethyl maleate), dialkyl furnarates, etc, and rubber-resin blends such as blends of butadiene-styrene rubbery copolymers with butadiene-styrene resinous copolymers, blends of butadiene-acrylonitrile rubbery copolymers with styrene-acrylonitrile resinous copolymers, blends of polyvinyl chloride and butadiene-acrylonitrile rubbery copolymers, etc. If oil resistance is desired, as where the coated fabric is employed for waterproof Work clothing, a sealing material such as neoprene is preferred. Although plasticized polyester resins such as alkyl resins, etc. could be em ployed, such resins are excluded in the preferred form of this invention as they contain isocyanate reactive groups. The preferred sealing materials are flexible elasto-mersthat are free of both isocyanate groups and isocyanate reactive groups. This will be seen to also exclude other elastomers containing active hydrogen atoms such as aldehyde treated material and synthetic rubbers, for example, those disclosed in U.S. Patents 1,915,808 and 1,640,363 and British Patent 486,878, rubber di(hydroxyphenyl), and hydroxylated rubbers, e.g., the peracetylated rubbers and hydroylzed peracetylated rubbers described in U.S. Patent 1,988,448. The presence of active hydrogen containing groups (isocyanate-reactive) is determinable by means of the Zereivitinoff test, Berichte 40, 2023 (1907).

As shown in FIGURE 2, the sealing material 12 is applied to one side of the fabric so as to penetrate or impregnate the interstices between the individual filaments as well as between the individual yarns at 13. As the sealing material is free of isocyanate radicals, it does not form a chemical bond with the amide or hydroxyl group-containing fabric as would polyurethane compositions. The sealing material being more or less elastic and yielding permits the necessary slight movement between the yarns in the fabric under stress. The sealing materialmay be applied by spreading or calendering. The coated fabric may be heated to dry or cure the sealing material either before or after the application of the polyurethane coating.

For purposes of this invention, the polyurethane elastomeric composition -14 is composed of the reaction product of an organic polyisocyanate (preferably an organic diisocyanate) and a hydroxy-terminated material selected from the group consisting of polyesters having a molecular Weight of from 1000 to 4000 and having an acid number of less than 6, and polyethers having a molecular weight of from 500 to 30 00 and having the ether linkages thereof separated by linear alkyl hydrocarbon chains of from two to five carbon atoms. The polyesters are typically produced from the reaction of a polycarboxylic acid (preferably a dicarboxylic acid or anhydride thereof) with a polyhydric alcohol (preferably a glycol). Sufficient polyisocyanate is employed to insure that the resulting polyurethane composition has unreacted isocyanate groups so that such composition will form a chemical bond with the fibers of the fabric containing isocyanate reactive groups.

Considering in more detail the basic starting materials of the polyurethane elastomer, the polyester employed is typically an anhydrous polyester made from a saturated glycol, for example ethylene glycol, and an aliphatic dicarboxylic acid or anhydride thereof, for example, adipic acid, using an excess of glycol over the acid so that the resulting polyester is substantially terminated with alcoholic hydroxyl groups. Such an amount of glycol is used as to give a polyester having a hydroxyl number of 112 to 28 and preferably 112 to 37, and a low acid number of less than 6 and preferably less than 2. The polyesters are substantially linear in type with melting point levels of 90 C. or lower. The molecular weight is within the range from 1000 to 4000 and preferably from 1000 to 3000. Many of the useful polyesters were obtained by a condensation reaction of one or more .saturated alkyl dibasic acids or acid anhydrides with one or more saturated glycols. Thus, for example, good results have been obtained using poly (ethylene-propylene adipate), having a molecular weight between 1900 and 2000, and formed by esterifying a mixture of ethylene glycol and propylene glycol in a mol ratio of 70 to 30, respectively, with adipic acid. Other examples of suitable polyesters are polyethylene adipate, polyethylene adipate (70)-phthalate (30), poly (diethylene glycol adipate), poly (triethylene glycol adipate), etc.

As an alternative to the polyesters just described, there may be used one or more members of the class of elastomer-yielding polyethers. The polyethers are typified by an anhydrous, chain-extended polyether possessing ether linkages (O) separated by aliphatic hydrocarbon chains. The ether contains terminal alcoholic hydroxyl groups reactive with isocyanate groups. The polyethers used are substantially linear in type with melting point levels of 90 C. or lower. The molecular weight of the polyethers is within the range of 500 to 3000 (i.e., hydroxyl number of about 225 to 37) and preferably within the range of 75-0 to 2500 (i.e., hydroxyl number of about 150 to 45). Examples of such polyethers are polyethylene glycol, poly (trimethylene glycol), poly (tetramethylene glycol), poly (pentamethylene glycol), poly (Z-ethyl 1,3-propylene glycol), and poly (Z-methyl 1,5-amylene glycol). In general, polyethers having the ether linkages thereof separated by linear aliphatic hydrocarbon chains of from two to five carbon atoms can be employed.

As employed herein, the expression linear is intended to include bivalent aliphatic or aromatic radicals directly connecting the carbonyloxy groups of the polyester or oxygen atoms of the polyether, with or without non-functional lower alkyl side chains. In the case of polyethers, said non-functional lower alkyl side chains should be attached to a carbon atom other than the terminal carbon atoms of the bivalent radical.

Any of a wide variety of conventional organic diisocyanates may be employed. Such organic diisocyanates can be divided into the following sub-classes of (a) alkylene, (12) arylene, (c) aralkylene, and (d) alkarylene diisocyanates. Examples of the subclasses are the alkylene diisocyanates such as 1,6-hexamethylene diisocyanate, 1,4- tetramethylene diisocyanate, 1,10-decamethylene, diisocyanate, and including cycloalkylene diisocyanates such as 1,4-cyclohexylene diisocyanate and 4,4'-methylene-bis- (cyclohexyl isocyanate); the arylene diisocyanates such as m-phenylene diisocyanate, p-phenylene diisocyanate, p,p-biphenyl diisocyanate, 1,5-naphthalene diisocyanate, 4-chloro-l,3-phenylene diisocyanate, and 1,5-tetrahydronaphthalene diisocyanate; aralkylene diisocyanates such as metaxylylene diisocyanate; and alkarylene diisocyanates such as 2,4-toluene diisocyanate and p,p-diphenylmethane diisocyanate. It is preferred to use a molar excess of diisocyanate, commonly from 20% to 250% molar excess, over that amount which would be required to react with all of the alcoholic hydroxyl groups furnished by the polyester or polyether, as the case may be. The reaction is frequently effected by heating a mixture of the polyester or polyether and the diisocyanate under anhydrous conditions at an elevated temperature, e.g., 70150 C., to form an uncured liquid material which is a linear polyurethane having terminal isocyanate groups. The liquid material may then be cured with an agent capable of forming urea linkages in the polymer, such as aromatic diamines (p,p-diaminodiphenyl methane or pphenylene diamine), amino-phenols (p-aminophenol or m-aminophenol), aliphatic diamines (hexamethylene-diamine or tetram-ethylene diamine), amino-alcohols (ethanolamine or p-aminobenzyl alcohol) or water. Diter-tiaryalkyl peroxides and dicumyl peroxide may also be employed as curing agents.

The liquid polyurethane composition (uncured) may be applied to the fabric after it has been coated with a sealing material by brushing, spraying, spreading or calendering and thereafter heated to cure the same. As shown in FIGURE 2, the polyurethane 14 only bonds to the tops of the fabric filaments due to the presence of sealing material 12.

The following example will serve to illustrate the invention in more detail. A nylon fabric having continuous, essentially untwisted filaments composed of polyhexamethylene adiparnide was employed. The size of the yarn was 210 denier in both the warp and weft. The fabric had 40 warps per inch, 40 wefts per inch, and a weight of 2.29 oz./sq. yd. The thickness of the fabric was .0054 inch and the ratio of width to thickness was 7.00 in the warp and 7.85 in the weft. The fabric is then coated with neoprene (polychloroprene) on one side by spreading. The neoprene employed had the following composition in parts by weight:

Polychloroprene 100 Zinc oxide 10 Sulfur 2 Calcined magnesia 10 Phenylbetanaphthylamine 2 Moles Propylene glycol 11 Ethylene glycol 4.25 Adipic acid 11.25

In the course of the preparation of the polyester the unreacted glycol is removed by vacuum distillation, and the extent of the distillation determines the molecular weight of the polyester, as calculated from the acid number and the hydroxyl number. The polyester used in this example has a molecular weight of about 2,000, a hydroxyl number of about 52 and an acid number of about 1.5.

To make the liquid prepolymer, 1 mole of the foregoing polyester is mixed with 2 moles of p,p-diphenylmethane diisocyanate, the mixture being reacted at C. for 1% hours to yield a curable material having terminal isocyanate groups capable of reacting with agents containing active hydrogen atoms.

A dispersion or suspension is then prepared by mixing parts by weight (or, suitably, from 50 to parts) of powdered 3,3-tdichloro-4,4-diaminodiphenylmethane in 100 parts of polypropylene glycol having a molecular weight of about 2,000. These materials may be mixed on a 3 roll paint mill to form a smooth, uniform paste from which the diamine has no undesirable tendency to settle out, and which is readily miscible with the prepolymer.

About 10 parts (or about 5 to 25 parts) of the diamine dispersion in polypropylene glycol is then mixed intimately with 100 parts of the described prepolymer at a temperature of 70 C.

After preheating the fabric at 250 F. for 5 minutes to remove moisture, the nylon fabric coated on one side with neoprene was then further coated by spreading a 90% non-aqueous solution of the polyurethane intermediate in acetone on the other side. After allowing the solvent to evaporate, the coated fabric was heated at 305 F. for 15 minutes to cure the polyurethane intermediate. The resulting coated fabric was fabricated into waterproof work clothing which displayed excellent tear resistance and abrasion resistance.

Besides being useful for fabricating waterproof work clothing, the coated fiabric of the instant invention may be used for flexible gasoline tanks, electrical insulating tape, awning and tarpaulin material, gloves and other related applications.

hile the preferred form of this invention has been described herein, it will be understood that changes in the details thereof may be made without departing from the spirit of this invention, and it is intended to cover all those changes which come within the scope of the appended claims.

Having thus described my invention, what I claim and desire to protect by Letters Patents is:

1. A coated fabric having both tear resistance and abrasion resistance formed of a fabric woven from yarns of continuous, essentially untwisted filaments, said filaments being composed of organic fibers containing a plurality of isocyanate-reactive groups, a flexible elastomeric sealing material free of isocyanate groups applied to one side of said fabric so as'to penetrate the interstices thereof, and a polyurethane elastomeric composition applied to'the other side of said fabric so as to adhere thereto, said adhesion being limited to the tops of the filaments by the sealing material.

2. A coated fabric as defined in claim 1 wherein said sealing material is free of both isocyanate groups and isocyanate-reactive groups.

3. A coated fabric as defined in claim 1 wherein said filaments are composed of organic fibers containing more than two isocyanate-reactive groups having at least one active hydrogen atom selected from the group consisting of amide groups and hydroxyl groups, and wherein said yarns have a greater width than thickness.

4. A coated fabric as defined in claim 1 wherein said filaments are composed of organic fibers containing a plurality of isocyanate-reac'tive groups selected from the group consisting of nylon, silk, casein fibers, rayon and high strength regenerated cellulose.

5. A coated fabric formed of a fabric woven from yarns of continuous, essentially tin-twisted polyhexamethylene adipam-ide filaments, neoprene app-lied to one side of said fabric so as to penetrate the interstices thereof, and a polyurethane elastomeric composition containing unreacted isocyanate groups applied to the other side of saidfabric so as to adhere thereto, said adhesion being limited to the tops of the filaments.

6. A method of making a coated fabric having both tear resistance and abrasion resistance comprising the steps of applying a flexible elastomeric sealing material free of isocyanate groups to one side of a fabric so as to penetrate the interstices thereof, said fabric being woven from yarns of continuous, essentially untwisted filaments composed of organic fibers containing a plurality of isocyanate-reactive groups, and thereafter applying a polyurethane composition to the other side of said fabric so as to adhere thereto, said adhesion being limited to the tops of said filaments by said sealing material.

7. A method of making a coated fabric as defined in claim 6 wherein said sealing material is free of isocyanatereactive groups.

8. A method of making a coated fabric as defined in claim 6 wherein said filaments are composed of organic fibers containing a plurality of isocyanate-reactive groups selected from the group consisting of linear synthetic polyamides having recurring carbonamide groups as an integral part of the main polymer chain, silk, casein fibers, rayon and high strength regenerated cellulose.

9. A method of making a coated fabric comprising the steps of applying neoprene to one side of a fabric so as to penetrate the interstices thereof, said fabric being woven from yarns of continuous, essentially untwisted nylon filaments, and thereafter applying a polyurethane composition to the other side of said fabric so as to adhere thereto, said adhesion being limited to the tops of the filaments.

References Cited in the file of this patent UNITED STATES PATENTS 2,721,811 Dacey et a1. Oct. 25, 1955 2,766,164 Salem Oct. 9, 1956 FOREIGN PATENTS 1,066,986 Germany Oct. 15, 1959 

1. A COATED FABRIC HAVING BOTH TEAR RESISTANCE AND ABRASION RESISTANCE FORMED OF A FABRIC WOVEN FROM YARNS OF CONTINUOUS, ESSENTIALLY UNTWISTED FILAMENTS, SAID FILAMEANS BEING COMPOSED OF ORGANIC FIBERS CONTAINING A PLURALITY OF ISOCYANATE-REACTIVE GROUPS, A FLEXIBLE ELASTOMERIC SEALING MATERIAL FREE OF ISOCYANATE GROUPS APPLIED TO ONE SIDE OF SAID FABRIC SO AS TO PENETRATE THE INTERSTICES THEREOF, AND A POLYURETHANE ELASTOMERIC COMPOSITION APPLIED TO THE OTHER SIDE OF SAID FABRIC SO AS TO ADHERE THERETO, SAID ADHESION BEING LIMITED TO THE TOPS OF THE FILAMENTS BY THE SEALING MATERIAL. 